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  77 Replaced and Removed Command Names
  
  In  general  we try to keep GAP 4 compatible with former releases as much as
  possible.  Nevertheless,  from  time  to time it seems appropriate to remove
  some  commands  or  to change the names of some commands or variables. There
  are  various  reasons  for  that:  Some  functionality  was improved and got
  another  (hopefully better) interface, names turned out to be too special or
  too  general  for  the  underlying  functionality,  or names are found to be
  unintuitive or inconsistent with other names.
  
  In  this  chapter  we  collect such old names while pointing to the sections
  which  explain  how to substitute them. Usually, old names will be available
  for  several  releases;  they may be removed when they don't seem to be used
  any more.
  
  The obsolete GAP code is collected in two library files, lib/obsolete.gd and
  lib/obsolete.gi.  By  default,  these files are read when GAP is started. It
  may be useful to omit reading these files, for example in order to make sure
  that  one's  own GAP code does not rely on the obsolete variables. For that,
  one  can  use  the  -O  command  line  option (see 3.1) or set the component
  ReadObsolete  in  the  file gap.ini to false (see 3.2). Note that -O command
  line option overrides ReadObsolete.
  
  (Note  that  the  condition  whether the library files with the obsolete GAP
  code  shall  be  read  has changed. In GAP 4.3 and 4.4, the global variables
  GAP_OBSOLESCENT  and  GAPInfo.ReadObsolete  –to  be set in the user's .gaprc
  file– were used to control this behaviour.)
  
  
  77.1 Group Actions – Name Changes
  
  The concept of a group action is sometimes referred to as a group operation.
  In  GAP 3  as well as in older versions of GAP 4 the term Operation was used
  instead  of  Action.  We decided to change the names to avoid confusion with
  the term operation as in DeclareOperation (79.18-6) and operations for Xyz.
  
  Here are some examples of such name changes.
  
        OLD                     │ NOW USE                      
        ────────────────────────┼─  
        Operation               │ Action (41.7-2)              
        RepresentativeOperation │ RepresentativeAction (41.6-1)
        OperationHomomorphism   │ ActionHomomorphism (41.7-1)  
        FunctionOperation       │ FunctionAction (41.12-4)     
  
  
  77.2 Package Interface – Obsolete Functions and Name Changes
  
  With  GAP 4.4  the  package  interface  was  changed. Thereby some functions
  became obsolete and the names of some others were made more consistent.
  
  The    following   functions   are   no   longer   needed:   DeclarePackage,
  DeclareAutoPackage,              DeclarePackageDocumentation             and
  DeclarePackageAutoDocumentation.  They  are  substituted  by  entries in the
  packages' PackageInfo.g files, see 76.3-12.
  
  Furthermore,  the  global  variable  PACKAGES_VERSIONS  is no longer needed,
  since  this  information is now contained in the GAPInfo.PackagesInfo record
  (see  3.5-1).  The global variable Revisions is also no longer needed, since
  the function DisplayRevision was made obsolete in GAP 4.5.
  
  The following function names were changed.
  
        OLD            │ NOW USE               
        ───────────────┼─  
        RequirePackage │ LoadPackage (76.2-1)  
        ReadPkg        │ ReadPackage (76.3-1)  
        RereadPkg      │ RereadPackage (76.3-1)
  
  
  77.3 Normal Forms of Integer Matrices – Name Changes
  
  Former  versions  of  GAP 4  documented  several functions for computing the
  Smith  or  Hermite  normal form of integer matrices. Some of them were never
  implemented  and  it was unclear which commands to use. The functionality of
  all  of these commands is now available with NormalFormIntMat (25.2-9) and a
  few interface functions.
  
  
  77.4 Miscellaneous Name Changes or Removed Names
  
  In  former  releases of GAP 4 there were some global variable names bound to
  general  information  about  the  running GAP, such as path names or command
  line options. Although they were not officially documented they were used by
  several  users  and in some packages. We mention here BANNER and QUIET. This
  type of information is now collected in the global record GAPInfo (3.5-1).
  
  Here are some further name changes.
  
        OLD                     │ NOW USE                        
        ────────────────────────┼─  
        MonomialTotalDegreeLess │ MonomialExtGrlexLess (66.17-14)
        NormedVectors           │ NormedRowVectors (61.9-11)     
        MutableIdentityMat      │ IdentityMat (24.5-1)           
        MutableNullMat          │ NullMat (24.5-2)               
  
  The  operation  PositionFirstComponent  has  been  deprecated in GAP 4.8 and
  later  due  to  issues with its documentation and implementation. Instead of
  PositionFirstComponent(list,obj),  you may use PositionSorted(list,[obj]) or
  PositionProperty(list,x->x[1]=obj)  as  a  replacement,  depending  on  your
  specific use case.
  
  77.4-1 InfoObsolete
  
  InfoObsolete info class
  
  is  an  info class to display warnings when an obsolete variable is used. By
  default, these warnings are switched off since the info level for this class
  is  0.  Setting  it  to  1  will trigger warnings if GAP will detect that an
  obsolete  variable  is used at runtime (this detection is possible, however,
  only for obsolete variables declared using DeclareObsoleteSynonym).
  
  To  check  that  the GAP code does not use obsolete variables at the parsing
  time, and not at a runtime, use -O command line option, see 3.1.
  
  
  77.5 The former .gaprc file
  
  Up to GAP 4.4, a file .gaprc in the user's home directory (if available, and
  GAP  was  started  without -r option) was read automatically during startup,
  early enough for influencing the autoloading of packages and late enough for
  being  allowed  to  execute  any GAP code. On Windows machines this file was
  called gap.rc.
  
  In GAP 4.5 the startup mechanism has changed, see 3.2 for details. These new
  configuration files are now contained in a directory GAPInfo.UserGapRoot.
  
  For  the  sake  of  partial  backwards  compatibility,  also the former file
  ~/.gaprc  is still supported for such initializations, but this file is read
  only  if  the directory GAPInfo.UserGapRoot does not exist. In that case the
  ~/.gaprc  is  read  at the same time as gaprc would be read, i. e., too late
  for influencing the startup of GAP.
  
  As before, the command line option -r disables reading ~/.gaprc, see 3.1.
  
  To  migrate from the old setup to the new one introduced with GAP 4.5, first
  have  a  look  at the function WriteGapIniFile (3.2-3). Many users will find
  that  all  or  most of what was set in the old ~/.gaprc file can now be done
  via  the  user  preferences  in  a  gap.ini  file.  If  you had code for new
  functions  or  abbreviations  in  your old ~/.gaprc file or you were reading
  additional  files,  then  move this into the file gaprc (without the leading
  dot,   same   name   for   all   operating   systems)   in   the   directory
  GAPInfo.UserGapRoot.
  
  
  77.6 Semigroup properties
  
  Until  Version  4.8  of  GAP  there  was  inconsistent  use of the following
  properties   of  semigroups:  IsGroupAsSemigroup,  IsMonoidAsSemigroup,  and
  IsSemilatticeAsSemigroup.  IsGroupAsSemigroup  was  true for semigroups that
  mathematically  defined  a group, and for semigroups in the category IsGroup
  (39.2-7);  IsMonoidAsSemigroup  was  true for semigroups that mathematically
  defined  monoids,  but did not belong to the category IsMonoid (51.2-1); and
  IsSemilatticeAsSemigroup  was  simply  a property of semigroups, there is no
  category IsSemilattice.
  
  From Version 4.8 onwards, IsSemilatticeAsSemigroup is renamed IsSemilattice,
  and IsMonoidAsSemigroup returns true for semigroups in the category IsMonoid
  (51.2-1).
  
  77.6-1 IsSemilatticeAsSemigroup
  
  IsSemilatticeAsSemigroup( S )  property
  
  IsSemilatticeAsSemigroup  returns  true  if the semigroup S is a semilattice
  and false if it is not.
  
  A  semigroup  is  a semilattice if it is commutative and every element is an
  idempotent. The idempotents of an inverse semigroup form a semilattice. This
  is identical to IsSemilattice (IsSemilattice???) # and is present in GAP 4.8
  #  only for the sake of compatibility with beta-releases. # It should not be
  used in new code.

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